Mueller told delegates that the OTW MAS device was similar to Bard Electrophysiology’s High-Density Mesh Ablation System (HDMAS), which combines electrophysiological mapping, cardiac stimulation, and radiofrequency ablation in one device. He said: “The mesh electrode is identical in design and construction to the HDMAS catheter and it has the same 30mm deployed diameter.” However, he added that there were differences-the OTW MAS only had one large fluoroscopic marker positioned at pole one to improve orientation and visibility, a shorted mesh structure to improve vein access, and real-time graphics could be displayed on Bard’s TEMPULSE radiofrequency controller to “optimise feedback during ablation.” Mueller reported that the aim of the GENESIS study was to confirm safety and the short- and long-term effectiveness of the OTW MAS device for the management of symptomatic paroxysmal atrial fibrillation.

Patients were included in the study if they were older than 18 years, had had a minimum of two episodes of atrial fibrillation within the last 12 months, and had failed on at least one class I–IV antiarrhythmic drug. They were excluded if they had persistent or permanent atrial fibrillation, were unable to be adequately anticoagulated, had an intracardiac thrombus, left atrial diameter of >50mm, had undergone previous ablation of the left atrium to treat atrial fibrillation, had a known bleeding disorder, or a contraindication to transseptal access. According to Mueller, the definition of acute procedural success with the system “was pulmonary vein isolation of all pulmonary veins with the OTW MAS device alone. The use of a catheter other than the OTW MAS to achieve pulmonary vein isolation was considered acute procedural failure and the creation of lesions other than in the pulmonary vein in the left atrium was also considered acute procedural failure.” He added the long-term success was defined as freedom from symptomatic recurrent paroxysmal atrial fibrillation, atrial flutter, or atrial tachycardia for more than 30 seconds 91–365 days after the procedure (there was a blanking period of 90 days). Patients were followed for 12 months.

At present, of the 42 patients enrolled in the study, the investigators have 30-day data (in the blanking period) for 30 of them. Mueller said that in the silent veins that were not counted as isolated, as there was no rule how to proceed with them in the protocol, the OTW MAS was associated with an acute procedural success rate of 83.3%. Also, the system was associated with an acute procedural success rate of 93.3% if the silent veins were taken out of the analysis. Mueller reported that the total procedural time with the device was 161.8 minutes; the total ablation time was 46.2 minutes, the total fluoroscopy time was 32 minutes, and there were four re-ablations during the blanking period. Mueller commented: “Compared with the STOP AF trial, which also documented the first experience with a new ablation device [Arctic Front, Medtronic], I think these data compare pretty well. The success rates are also comparable.” To date, the rate of freedom of atrial fibrillation is 74%. He added that there was one device-related episode of recurrent atrial fibrillation and two device-related incidences of bleeding complications.

Mueller concluded: “The usability of the new system has been validated-problems with the system and hardware identified in the study have been implemented. The early data are encouraging with respect to outcomes and procedure endpoints. The adverse events might be reduced with different patient selection-ie, some patients with a history of radiation would be excluded from this device.”